:root {
  --bg: #070a14;
  --panel: rgba(13, 18, 34, 0.78);
  --panel-border: rgba(140, 160, 200, 0.12);
  --panel-border-strong: rgba(140, 160, 200, 0.22);
  --text: #e9ecf5;
  --text-dim: #8a94ac;
  --text-subtle: #5a6680;
  --accent: #89c9ff;
  --col-G: #f6c667;
  --col-eps: #6be1c7;
  --col-n: #c89bf5;
  --col-dt: #80e0a3;
  --serif: 'Instrument Serif', 'Iowan Old Style', Georgia, serif;
  --sans: 'IBM Plex Sans', -apple-system, system-ui, sans-serif;
  --mono: 'JetBrains Mono', 'SF Mono', Menlo, monospace;
}
* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0; height: 100vh; width: 100vw;
  overflow: hidden;
  background: radial-gradient(ellipse at 30% 20%, #101832 0%, var(--bg) 55%, #03050c 100%);
  color: var(--text);
  font-family: var(--sans);
  font-size: 14px;
  -webkit-font-smoothing: antialiased;
}
#canvas {
  position: absolute; inset: 0; width: 100%; height: 100%;
  display: block; z-index: 0;
  cursor: grab; touch-action: none;
}
#canvas.grabbing { cursor: grabbing; }

.topbar {
  position: absolute; top: 0; left: 0; right: 0; z-index: 10;
  padding: 18px 26px 24px;
  display: flex; align-items: baseline; gap: 20px;
  background: linear-gradient(to bottom, rgba(7,10,20,0.85), transparent);
  pointer-events: none;
}
.topbar > * { pointer-events: auto; }
.topbar .brand {
  font-family: var(--serif); font-style: italic;
  font-size: 28px; line-height: 1; letter-spacing: -0.01em;
}
.topbar .tagline {
  font-weight: 300; font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.22em;
  color: var(--text-subtle); margin-left: 4px;
}
.spacer { flex: 1; }

button, select {
  background: rgba(22, 28, 48, 0.75);
  color: var(--text);
  border: 1px solid var(--panel-border-strong);
  padding: 8px 14px; border-radius: 4px;
  font-size: 12px; font-family: var(--sans);
  letter-spacing: 0.04em; cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  text-transform: uppercase;
}
button:hover, select:hover {
  background: rgba(35, 45, 70, 0.85);
  border-color: rgba(137, 201, 255, 0.45);
}
button.primary {
  background: rgba(137, 201, 255, 0.12);
  border-color: rgba(137, 201, 255, 0.45);
  color: var(--accent);
}
button.icon {
  padding: 6px 10px;
  font-size: 14px; line-height: 1;
  letter-spacing: 0;
}
select {
  appearance: none; -webkit-appearance: none;
  padding-right: 30px;
  background-image: linear-gradient(45deg, transparent 50%, var(--text-dim) 50%), linear-gradient(135deg, var(--text-dim) 50%, transparent 50%);
  background-position: calc(100% - 15px) 50%, calc(100% - 11px) 50%;
  background-size: 4px 4px, 4px 4px;
  background-repeat: no-repeat;
}

.panel {
  position: absolute; top: 80px; right: 24px; bottom: 24px;
  width: 460px; z-index: 10;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 6px;
  backdrop-filter: blur(14px) saturate(1.2);
  -webkit-backdrop-filter: blur(14px) saturate(1.2);
  overflow-y: auto;
  box-shadow: 0 20px 60px -20px rgba(0,0,0,0.8);
}
.panel::-webkit-scrollbar { width: 6px; }
.panel::-webkit-scrollbar-track { background: transparent; }
.panel::-webkit-scrollbar-thumb { background: rgba(140,160,200,0.2); border-radius: 3px; }
.panel-inner { padding: 24px 26px 28px; }

.minimize {
  position: absolute; top: 10px; right: 12px;
  background: transparent; border: none;
  color: var(--text-subtle);
  padding: 4px 10px; font-size: 18px; line-height: 1;
  text-transform: none; letter-spacing: 0;
}
.minimize:hover { color: var(--text); background: transparent; border-color: transparent; }
.panel.collapsed { bottom: auto; height: 44px; overflow: hidden; }
.panel.collapsed .panel-inner { display: none; }

.section {
  margin-bottom: 28px; padding-bottom: 24px;
  border-bottom: 1px solid var(--panel-border);
}
.section:last-child { border-bottom: none; padding-bottom: 0; }
.section-head { display: flex; align-items: baseline; gap: 10px; margin-bottom: 10px; }
.section-num {
  font-family: var(--mono); font-size: 10px;
  color: var(--text-subtle); letter-spacing: 0.1em;
}
.section h2 {
  margin: 0; font-family: var(--serif); font-style: italic;
  font-size: 22px; font-weight: 400; line-height: 1.1;
  letter-spacing: -0.01em;
}
.section p {
  margin: 6px 0 0 0;
  color: var(--text-dim); line-height: 1.55;
  font-weight: 300; font-size: 13px;
}
.section p em { font-family: var(--serif); font-style: italic; color: var(--text); font-size: 15px; }

.formula {
  margin: 14px 0 12px 0; padding: 16px 10px;
  background: linear-gradient(180deg, rgba(5, 8, 18, 0.5), rgba(5, 8, 18, 0.2));
  border: 1px solid var(--panel-border);
  border-radius: 4px;
  overflow-x: auto; overflow-y: hidden;
  text-align: center;
}
.formula::-webkit-scrollbar { height: 4px; }
.formula::-webkit-scrollbar-thumb { background: rgba(140,160,200,0.15); }
.formula .katex { font-size: 1.2em; }
.formula .katex-display { margin: 0.3em 0; }

.katex .tw-G,  .katex .tw-G *   { color: var(--col-G); }
.katex .tw-eps,.katex .tw-eps * { color: var(--col-eps); }
.katex .tw-n,  .katex .tw-n *   { color: var(--col-n); }
.katex .tw-dt, .katex .tw-dt *  { color: var(--col-dt); }
.katex .tw-G, .katex .tw-eps, .katex .tw-n, .katex .tw-dt {
  cursor: pointer; position: relative; transition: filter 0.15s;
  border-bottom: 1px dashed currentColor;
  padding-bottom: 1px;
}
.katex .tw-G:hover, .katex .tw-eps:hover, .katex .tw-n:hover, .katex .tw-dt:hover {
  filter: brightness(1.3) drop-shadow(0 0 6px currentColor);
}

.legend {
  display: flex; flex-wrap: wrap; gap: 6px 12px; justify-content: center;
  font-family: var(--mono); font-size: 11px;
  margin-top: 8px; color: var(--text-subtle);
}
.legend .val { color: var(--text); font-weight: 500; }

.slider-group { margin: 14px 0 4px 0; }
.slider-row {
  display: grid; grid-template-columns: 72px 1fr 68px;
  align-items: center; gap: 12px;
  padding: 6px 8px; margin: 2px -8px;
  border-radius: 3px;
  transition: background 0.18s;
}
.slider-row.highlight { background: rgba(255, 255, 255, 0.04); }
.slider-row.pulse { animation: pulse 0.6s ease; }
@keyframes pulse {
  0%   { background: rgba(137, 201, 255, 0); }
  40%  { background: rgba(137, 201, 255, 0.22); }
  100% { background: rgba(137, 201, 255, 0); }
}
.slider-row label {
  font-family: var(--serif); font-style: italic;
  font-size: 18px; line-height: 1;
}
.slider-row label .hint {
  display: block; font-family: var(--mono); font-style: normal;
  font-size: 9px; color: var(--text-subtle);
  letter-spacing: 0.08em; text-transform: uppercase; margin-top: 2px;
}
.slider-row input[type=range] {
  -webkit-appearance: none; appearance: none;
  width: 100%; height: 2px;
  background: rgba(140, 160, 200, 0.18);
  border-radius: 1px; outline: none; margin: 0;
}
.slider-row input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 12px; height: 12px;
  background: var(--slider-color, var(--accent));
  border-radius: 50%; cursor: pointer;
  border: 2px solid #0a0f1e;
  box-shadow: 0 0 0 1px var(--slider-color, var(--accent)), 0 0 8px var(--slider-color, var(--accent));
  transition: transform 0.12s;
}
.slider-row input[type=range]:hover::-webkit-slider-thumb { transform: scale(1.3); }
.slider-row input[type=range]::-moz-range-thumb {
  width: 12px; height: 12px;
  background: var(--slider-color, var(--accent));
  border-radius: 50%; cursor: pointer;
  border: 2px solid #0a0f1e;
}
.slider-row .value {
  font-family: var(--mono); font-size: 11.5px;
  text-align: right; white-space: nowrap;
}
/* Typable value field. Looks like the old read-only value display, but you
   can click and edit. Spinners hidden. */
.slider-row input.value {
  background: transparent;
  border: 1px solid transparent;
  color: var(--text);
  padding: 2px 4px;
  border-radius: 3px;
  width: 68px;
  outline: none;
  -moz-appearance: textfield;
}
.slider-row input.value::-webkit-outer-spin-button,
.slider-row input.value::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.slider-row input.value:hover {
  background: rgba(140, 160, 200, 0.06);
  border-color: var(--panel-border);
}
.slider-row input.value:focus {
  background: rgba(137, 201, 255, 0.06);
  border-color: rgba(137, 201, 255, 0.45);
}

.footnote {
  font-size: 11.5px; line-height: 1.55;
  color: var(--text-subtle); margin-top: 10px; font-weight: 300;
}
.footnote strong { font-weight: 500; }

.stats {
  position: absolute; left: 24px; bottom: 24px; z-index: 10;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 6px;
  padding: 14px 18px;
  font-family: var(--mono); font-size: 10.5px;
  backdrop-filter: blur(14px) saturate(1.2);
  -webkit-backdrop-filter: blur(14px) saturate(1.2);
  min-width: 170px;
  display: none;
}
.stats.visible { display: block; }
.stats .title {
  font-family: var(--sans); font-size: 9px;
  letter-spacing: 0.22em; text-transform: uppercase;
  color: var(--text-subtle); margin-bottom: 8px;
}
.stats .stat-row { display: flex; justify-content: space-between; gap: 20px; padding: 3px 0; }
.stats .stat-row .k { color: var(--text-subtle); }

@media (max-width: 960px) {
  .topbar { padding: 14px 16px 20px; flex-wrap: wrap; gap: 10px; }
  .topbar .tagline { display: none; }
  .panel {
    width: calc(100% - 20px);
    right: 10px; left: 10px; bottom: 10px; top: auto;
    max-height: 65vh;
  }
  .stats { display: none; }
}